Post Office workers and managers across the country will stage a fresh strike Monday in a dispute over jobs, pensions and branch closures.
Members of the Communication Workers Union and Unite will walk out for the second time in as many months, with further action closer to Christmas not ruled out.
The unions are in dispute over the closure of the final salary pension scheme, job losses, and the franchising of Crown Post offices, the larger branches usually found in high streets.
The Post Office said that most of its branches will not be affected by the action, but the dispute affects thousands of staff working across the UK.
The strike follows a walkout in September which the unions said was strongly supported.
CWU general secretary Dave Ward said: "The stakes have never been higher for the future of the Post Office, its workers and the communities they serve.
"The Post Office is at crisis point and the management and Government need to listen to the workforce.
"We are calling for the Government, as the owner of the Post Office, to step in, halt the cuts and work with us to develop a proper strategy that will secure the future of the service."
The Post Office maintains that moving post office services to retail outlets like high street chain WH Smith means longer opening hours.